16-05-2014, 03:45 PM
Different techniques of metal joining
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Objectives
• This chapter provides information on metal joining
processes, for example, fusion welding and other high
energy beam welding techniques.
• Students are required to indicate advantages and
disadvantages of different methods of metal joining.
• Students should be able to select appropriate methods of
metal joining for the required applications.
Blazing
• Blazing is similar to soldering but uses fillers of
higher Tm (450-800oC).
• Give better strength than soldering but might get
oxidation problems or discoloration.
• Heating methods such as gas torch, furnace, molten-
flux bath, induction heating resistance heating are used.
Gas welding
• Gas welding is a welding process that
melts and joints metals by heating them
with a flame caused by a reaction of fuel
gas and oxygen.
• The most commonly used method is
Oxyacetylene welding, due to its high
flame temperature.
• The flux may be used to deoxidize and
cleanse the weld metal.
• The flux melts, solidifies and forms a
slag skin on the resultant weld metal.
Plasma arc welding
Plasma arc welding (PAW) is a process that melts and joins metals by
heating them with a constricted arc established between a tungsten
electrode and the metals.
• PAW is similar to GTAW but an orifice gas
and an shielding gas is used.
• The arc is constricted due to the covering
action of the orifice gas nozzle.
• The tungsten electrode is recessed in the
orifice gas nozzle and the arc is initiated by
a high frequency generator between the
electrode tip and the water-cooled orifice
gas nozzle.
• The arc is then transferred to between the
electrode tip and the workpiece.